The invention relates to a fall arrester for a climbing protection system to prevent a person falling from a ladder, a platform or similar. The fall arrester runs in a guide rail. The person to be secured wears a safety belt and is connected to the fall arrester by a connection means. The fall arrester has a runner or carriage which runs in the guide rail. The runner has a housing and a pawl rotatably housed therein which is loaded by a spring. The spring presses the pawl into a locked position. In the event of a fall, the pawl then strikes against catching stops or a perforation in the guide rail. The connection means are secured at an attachment point of the pawl. For descent, the pawl is swivelled against the force of the spring into an unlocked position.
Such a fall arrester which is suitable for a climbing protection system is known from EP-A-0 168 021, DE-A-27 36 037 and DE-A-19 61 757. With these climbing protection systems, a guide rail with a C profile is used. The edges of the longitudinally-running opening of the C profile are the guide flanges on which the fall arrester is guided. In the rear wall of the C profile, catching stops are pushed out or recesses are punched, against which the pawl runs in the event of a fall so that arrest takes place in form-locking manner.
The pawl points downwards so that during ascent, the pawl travels over the catching stop or the perforation in the rear wall of the C profile. During descent along the ladder, the user leans backwards (back-pull) so that the pawl is pulled away from the rear wall of the guide rail and the carriage can travel downwards unimpeded.
With these fall arresters, the connection line of the fulcrum of the pawl and the attachment point form an acute angle of approx. 30xc2x0 to the horizontal, and the pawl is swivelled by approx. 25 to 30xc2x0 out of the completely unlocked position into the completely locked position. For reasons of operational safety, the pawl is pressed into the locked position by a relatively powerful spring. To distribute the load and the abrasion on the rollers, the fulcrum of the pawl is approximately in the centre between the two axes of the rollers.
In some cases, a descent with back-pull is not possible. To be able to climb through narrow manhole covers, shafts, cage ladders etc., the person ascending or descending must stay close to the ladder. As a result of the absence of back-pull, the pawl is pressed by the spring into the guide rail profile so that the fall arrester is held by the catching stops or the perforation in the rear wall of the guide rail, and descent is not possible. To use the fall arrester in such cases, special runners are used which are constructed such that the weight force of the body of the runner is greater than the force of the spring loading the pawl, so that the pawl is unlocked when the fall arrester is held at the attachment point.
A fall arrester is known in which, in the unlocked position, the attachment point lies above the horizontal passing through the fulcrum of the pawl. The fall arrester can be used only for descent without back-pull, as the pawl would be pulled into the locked position by the back-pull. The object of the invention is to provide a fall arrester with which ascent into narrow shafts is possible without problems (descent without back-pull), but which can also be used in conventional manner on ladders (descent with back-pull).
This object is achieved according to the invention in that the fall arrester is unlocked when the connection line between fulcrum of the pawl and attachment point forms an angle of less than 2xc2x0 to the horizontal and the spring exerts a torque on the pawl which is less than the torque produced by the weight of the fall arrester when the fall arrester is held at the attachment point.
If the two above-named conditions are combined in a fall arrester, the latter can be used universally in all conditions and simultaneously provides the user with the greatest comfort.
Upon descent with back-pull, an angle of approx. 2xc2x0 to the horizontal forms in the connection means, the person introducing a force of up to 600 N into the connection means. Because of differences in friction between runner and guide rail or the condition of the guide rail, this angle can be slightly smaller (0xc2x0) or larger (4xc2x0). If an unimpeded descent is now desired, the pawl must remain in this 0xc2x0 to 4xc2x0 range, drawn by the back-pull, in any case.
The attachment point of the pawl lies below the horizontal passing through the fulcrum of the pawl. Preferably, the connection line of attachment point and fulcrum of the pawl forms an angle of approx. 5xc2x0 to the horizontal when the pawl is in the unlocked position. The result of this is that, during descent with back-pull, the pawl is in the unlocked position in an operationally safe manner.
The pawl advantageously reaches the locked position through swivelling by only approx. 150xc2x0. The pawl projects so far from the underside of the runner that it strikes against the catching stops or the perforation in the rear wall of the guide rail. To achieve a sufficient displacement of the tip of the pawl between the unlocked and the locked position despite this relatively small swivel angle, the distance from the tip to the fulcrum is as great as possible. For this purpose, the fulcrum is advantageously located at the top end of the runner and the tip of the pawl at the bottom end.
Because of the small angle at which the attachment point lies below the horizontal at which in the unlocked position, and the small swivel angle between unlocked and locked positions, the horizontal path which the attachment point covers between both positions is very short. Despite the relatively slight force of the spring, full operational safety is therefore guaranteed.
Overall, the runner is an approximately rectangular housing with a central opening. The pawl is housed in the central opening rotatably about a horizontal rotational axis.
The fall arrester is guided by guide devices in the guide rail. The guide devices lie on the outside and inside at the guide flanges of the guide rail. The guide devices are provided at the top and bottom ends of the runner and can each, as known from DE 299 06 047, have two pairs of fixed rollers. Preferably, in the fall arrester according to the invention, two additional fixed rollers are provided which, during use, are located inside the guide rail, the fulcrum of the pawl lying approximately between these additional rollers and the guide device at the top end of the fall arrester.